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Answer: In Account B, update the transit gateway attachment. Attach the new subnet ID that is associated with us-west-2c to Account B's VPC.
The issue described involves a new subnet (10.0.3.0/24) in the us-west-2c Availability Zone that cannot communicate with other VPCs, despite sharing a route table with other subnets that can. The key to resolving this issue lies in ensuring that the transit gateway is aware of and can route traffic to this new subnet. Option B suggests updating the transit gateway attachment to include the new subnet ID associated with us-west-2c to Account B's VPC. This action would ensure that the transit gateway can route traffic to and from the new subnet, enabling communication with other VPCs. Option A is incorrect because simply adding the subnets as destinations in the route table without ensuring the transit gateway is properly attached to the new subnet will not resolve the issue. Option C is incorrect because creating a static route in the transit gateway route tables in Account A does not address the need to attach the new subnet to the transit gateway in Account B. Option D is incorrect because recreating propagation for the entire VPC CIDR block does not specifically address the issue with the new subnet in us-west-2c.
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A company has a transit gateway in AWS Account A, shared with other accounts using AWS Resource Access Manager (AWS RAM) to enable connectivity to multiple VPCs within the same AWS Region. AWS Account B has a VPC (10.0.0.0/16) with subnets 10.0.0.0/24 in us-west-2a and 10.0.1.0/24 in us-west-2b, both of which can communicate with other VPCs.
A network engineer adds two new subnets: 10.0.2.0/24 in us-west-2b and 10.0.3.0/24 in us-west-2c, all sharing a single route table with the default route 0.0.0.0/0 pointing to the transit gateway. While resources in subnet 10.0.2.0/24 can communicate with other VPCs, resources in subnet 10.0.3.0/24 cannot.
What steps should the network engineer take to enable communication between resources in subnet 10.0.3.0/24 and other VPCs?
A
In Account B, add 10.0.2.0/24 and 10.0.3.0/24 as the destinations to the route table. Use the transit gateway as the target.
B
In Account B, update the transit gateway attachment. Attach the new subnet ID that is associated with us-west-2c to Account B's VPC.
C
In Account A, create a static route for 10.0.3.0/24 in the transit gateway route tables.
D
In Account A, recreate propagation for 10.0.0.0/16 in the transit gateway route tables.
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